Polyurethanes, polyureas and other isocyanate-containing resins are widely used in numerous industries. These resins typically come in two categories, thermoset and thermoplastic. They are usually coreacted with an active hydrogen-containing material, such as an amine or glycol, to effect cure; this is particularly true for thermosets.
Some curing agents used in polyurethane and/or polyurea compositions have relatively high freezing points, which makes shipping and storage of these materials during the winter season problematic. The problem is compounded when the compositions include pigments. When certain curative/pigment blends have thawed from a frozen state, the solids separate and the quality of the pigment dispersed therein can be lost, as measured by the Hegman scale. The Hegman scale is a measurement of particle size, which is typically used to denote the degree of pigment dispersion. When a material completely loses its quality of dispersion (Hegman equals zero), the particle size of the material is generally about 100 microns or greater. Such a separated blend would need to be redispersed before it could be used. In cases where the pigment has undergone “hard settling”, the pigment cannot be redispersed and the blend is unusable.
There remains a continuing need for curative agents, particularly those in which a pigment is dispersed, that can withstand lower storage and shipping temperatures. In addition, it would be advantageous to provide such agents that, even if they became frozen, can be thawed and used without the need to redisperse the pigment; it would be further advantageous to provide such agents that do not experience any substantial change or sacrifice in the properties they impart to the prepolymer or resin into which they are incorporated.